Obtained by the method of termoextraction antigenic complex from Brucella cells in an L-form, the characteristic of its chemical composition. Performed electrophoretic fractionation of the resulting antigenic complex in the polyacrylamide gel blocks in the presence of sodium dodecyl sulfate. With the help of Western blot showed that immunoreactive protein had a diffuse fraction with a molecular mass of 67.5 to 75.5 kDa. A high activity and specificity of the antigenic complex in the reaction of immunodiffusion and interfacial precipitin test.